Channel equalizer and method of processing broadcast signal in DTV receiving system

ABSTRACT

A channel equalizer includes a first transformer, an estimator, an average calculator, a second transformer, a coefficient calculator, a compensator, and a third transformer. The first transformer converts normal data into frequency domain data, where a known data sequence is periodically repeated in the normal data. The estimator estimates channel impulse responses (CIR) during known data intervals adjacent to each normal data block. The average calculator calculates an average value of the CIRs. The second transformer converts the average value into frequency domain data. The coefficient calculator calculates equalization coefficients using the average value, and the compensator compensates channel distortion of each normal data block using the coefficients. The third transformer converts the compensated data block into time domain data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/938,700, filed on Jul. 10, 2013, now U.S. Pat. No. 9,185,413, whichis a continuation of U.S. patent application Ser. No. 13/718,738, filedon Dec. 18, 2012, now U.S. Pat. No. 8,526,508, which is a continuationof U.S. patent application Ser. No. 13/426,538, filed on Mar. 21, 2012,now U.S. Pat. No. 8,355,451, which is a continuation of U.S. patentapplication Ser. No. 13/241,181, filed on Sep. 22, 2011, now U.S. Pat.No. 8,204,137, which is a continuation of U.S. patent application Ser.No. 12/961,435, filed on Dec. 6, 2010, now U.S. Pat. No. 8,054,891,which is a continuation of U.S. patent application Ser. No. 11/674,099,filed on Feb. 12, 2007, now U.S. Pat. No. 7,876,835, which claims thebenefit of earlier filing date and right of priority to Korean PatentApplication Nos. 10-2006-0013128, filed on Feb. 10, 2006, and10-2006-0089736, filed on Sep. 15, 2006, and also claims benefit of U.S.Provisional Application No. 60/883,154, filed on Jan. 2, 2007, thecontents of which are all hereby incorporated by reference herein intheir entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a digital telecommunications system,and more particularly, to a channel equalizer and a method of processingbroadcast signal in DTV receiving system.

Discussion of the Related Art

Presently, the technology for processing digital signals is beingdeveloped at a vast rate, and, as a larger number of the population usesthe Internet, digital electric appliances, computers, and the Internetare being integrated. Therefore, in order to meet with the variousrequirements of the users, a system that can transmit diversesupplemental information in addition to video/audio data through adigital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the video/audio data. However, withthe advent of digital broadcasting, digital television receiving systemsthat receive only video/audio data are already supplied to the market.Therefore, the supplemental data that are transmitted through the samechannel as the video/audio data should not influence the conventionalreceiving systems that are provided in the market. In other words, thismay be defined as the compatibility of broadcast system, and thesupplemental data broadcast system should be compatible with thebroadcast system. Herein, the supplemental data may also be referred toas enhanced data. Furthermore, in a poor channel environment, thereceiving performance of the conventional receiving system may bedeteriorated. More specifically, resistance to changes in channels andnoise is more highly required when using portable and/or mobilereceiving systems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a channel equalizerand a method of processing broadcast signal in DTV receiving system thatsubstantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a digital broadcastsystem that is suitable for transmitting supplemental data and that ishighly resistant to noise.

A further object of the present invention is to provide a channelequalizer and a method of processing broadcast signal in DTV receivingsystem that can use pre-defined known data that are already known by areceiving system and/or a transmitting system, thereby enhancing thereceiving performance of the digital broadcast (or television) receivingsystem.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, achannel equalizer for use in a digital television (DTV) receiving systemincludes a first transformer, an estimator, an average calculator, asecond transformer, a coefficient calculator, a compensator, and a thirdtransformer. The first transformer converts normal data in a broadcastsignal into frequency domain data. A known data sequence is periodicallyrepeated in the normal data. The estimator estimates channel impulseresponses during intervals in which first and second known datasequences located before and after each normal data block in thebroadcast signal are received. The average calculator calculates anaverage value of the estimated channel impulses, and the secondtransformer converts the average value into frequency domain data. Thecoefficient calculator calculates equalization coefficients using theaverage value in the frequency domain. The compensator compensateschannel distortion of each normal data block in the frequency domain bymultiplying each normal data block with the equalization coefficients.Finally, the third transformer converts the compensated normal datablock into time domain data.

In another aspect of the present invention, a channel equalization foruse in a digital television (DTV) receiving system includes an overlapunit, a first transformer, an estimator, a second transformer, acalculator, a compensator, a third transformer, and a save unit. Theoverlap unit overlaps normal data in a broadcast signal at apredetermined overlap ratio. A known data sequence is periodicallyrepeated in the normal data. The first transformer converts theoverlapped normal data into frequency domain data. The estimatorestimates a channel impulse response using the known data sequence, andthe second transformer converts the estimated channel impulse responseinto frequency domain data. The calculator calculates equalizationcoefficients using the estimated channel impulse response in thefrequency domain. The compensator compensates channel distortion of thenormal data in the frequency domain by multiplying the normal data withthe equalization coefficients. The third transformer converts thecompensated normal data into time domain data, and the save unit savesthe compensated normal data in the time domain.

In another aspect of the present invention, a channel equalizer for usein a DTV receiving system includes an overlap unit, a first transformer,an estimator, an interpolator, a second transformer, a calculator, acompensator, a third transformer, and a save unit. The overlap unitoverlaps normal data in a broadcast signal at a predetermined overlapratio. A known data sequence is periodically repeated in the normaldata. The first transformer converts the overlapped normal data intofrequency domain data. The estimator estimates a first channel impulseresponse during a known data interval, and the interpolator estimates asecond channel impulse response during a normal data interval byinterpolating the first channel impulse response. The second transformerconverts the estimated second channel impulse response into frequencydomain data. The calculator calculates equalization coefficients usingthe second channel impulse response in the frequency domain. Thecompensator compensates channel distortion of the normal data in thefrequency domain by multiplying the normal data with the equalizationcoefficients. The third transformer converts the compensated normal datainto time domain data. Finally, the save unit saves the compensatedformal data in the time domain.

In another aspect of the present invention, a channel equalizer for usein a DTV receiving system includes an overlap unit, a first transformer,a compensator, a second transformer, a save unit, an error calculator, apadding unit, a third transformer, and a coefficient update unit. Theoverlap unit overlaps normal data in broadcast signal at a predeterminedoverlap ratio. A known data sequence is periodically repeated in thenormal data. The first transformer converts the overlapped normal datainto frequency domain data. The compensator compensates channeldistortion of the normal data in the frequency domain by multiplying thenormal data with equalization coefficients. The second transformerconverts the compensated normal data into time domain data. The saveunit saves the compensated normal data in the time domain. The errorcalculator calculates an error of the saved normal data using a decisionvalue of the saved normal data and the known data sequence. The paddingunit pads zeros into the error according to the overlap ratio. The thirdtransformer converts the zero-padded error into frequency domain data.The coefficient update unit updates the equalization coefficients basedon the zero-padded error in the frequency domain.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates an example of a data frame structure after datainterleaving in a digital broadcast transmitting system according to thepresent invention;

FIG. 2 illustrates an example of known data being periodicallytransmitted according to the present invention;

FIG. 3 illustrates a block diagram of a channel equalizer according to afirst embodiment of the present invention;

FIG. 4 illustrates a block diagram of a channel equalizer according to asecond embodiment of the present invention;

FIG. 5 illustrates a block diagram of a channel equalizer according to athird embodiment of the present invention;

FIG. 6 illustrates a block diagram of a channel equalizer according to afourth embodiment of the present invention;

FIG. 7 illustrates an example of a linear interpolation of aninterpolator shown in FIG. 6;

FIG. 8 and FIG. 9 illustrate examples of overlap & save processesaccording to an embodiment of the present invention;

FIG. 10 illustrates a block diagram of a channel equalizer according toa fifth embodiment of the present invention;

FIG. 11 illustrates a block diagram of a channel equalizer according toa sixth embodiment of the present invention;

FIG. 12 illustrates a block diagram of a channel equalizer according toa seventh embodiment of the present invention;

FIG. 13 illustrates a block diagram showing the structure of ademodulating unit included a digital broadcast receiving systemaccording to an embodiment of the present invention;

FIG. 14 illustrates a block diagram of a digital broadcast (ortelevision or DTV) transmitting system according to another embodimentof the present invention;

FIG. 15 illustrates a block diagram showing a general structure of ademodulating unit within a digital broadcast (or television or DTV)receiving system according to another embodiment of the presentinvention;

FIG. 16 illustrates a block diagram showing the structure of a digitalbroadcast (or television or DTV) receiving system according to anembodiment of the present invention; and

FIG. 17 illustrates a block diagram showing the structure of a digitalbroadcast (or television or DTV) receiving system according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather forecast, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitting system and thereceiving system. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data. The present invention relates to performingchannel equalization in a frequency domain by using the known data knownalready known by the transmitting system and receiving system. Morespecifically, in the digital broadcast receiving system that multiplexesand transmits the enhanced data having information with the main data,known data known that are already known by the transmitting system andreceiving system may be inserted in an enhanced data packet section andthen transmitted. In order to enhance the receiving performance, anerror correction signal having a higher performance than that of themain data section is applied to the data transmitted from the enhanceddata packet section. At this point, the known data may be inserted inthe enhanced data packet section in various formats. Additionally, theknown data may be used in the digital broadcast receiving system forcarrier recovery, frame synchronization recovery, and channelequalization processes.

FIG. 1 illustrates an example of a data frame structure corresponding tothe output of a data interleaver (not shown) in a digital broadcasttransmitting system according to the present invention. Particularly,FIG. 1 illustrates an example of a predetermined number of data packetsgathered (or grouped) so as to be divided in to head, body, and tailareas. Herein, the head, body, and tail areas are each divided in52-packet units. FIG. 1 illustrates an example of each area beingconfigured of 52 packets, because the data interleaver operatesperiodically after a cycle of 52 packets. With respect to the output ofthe data interleaver, the body area within the data frame is allocatedto include at least a portion or the entire area in which enhanced dataare consecutively outputted. In the body area, the known data areperiodically inserted at a constant rate. The head area is locatedbefore the body area, and the tail area is located after the body area.For example, referring to FIG. 1, the main data are not included in thebody area, and the known data are inserted after each 6-packet (orsegment) cycle. Furthermore, the known data are additionally inserted atthe beginning of the body area.

In this case, the body area may show a stronger receiving performance,since there is no interference from the main data. The enhanced data ofthe head and tail areas are mixed with the main data in accordance withthe output order from the data interleaver. Accordingly, the receivingperformance in the head and tail areas is more deteriorated than in thebody area. Therefore, when known data are inserted in the enhanced dataand then transmitted, and when consecutive and long known data are to beperiodically inserted in the enhanced data, the known data may beinserted in the body area. This is because, based upon the output orderof the data interleaver, the enhanced data are not mixed with the maindata. At this point, known data having a predetermined length may beperiodically inserted in the body area. However, it is difficult toperiodically insert known data in the head and tail areas, and it isalso difficult to insert consecutive and long known data. Therefore,FIG. 1 corresponds to an example of inserting short known data sequencesin the head and tail areas at frequent cycle periods.

FIG. 2 illustrates an example of a data structure having known datasequences of the same patterns periodically inserted therein and beingtransmitted. Referring to FIG. 2, the data correspond to one of enhanceddata, main data, and a combination of enhanced data and main data. Inthe present invention, in order to be differentiated with the knowndata, the above-described data will be referred to as general data forsimplicity. Accordingly, when the known data are regularly inserted inthe valid data as described above, the channel equalizer included in thedigital broadcast receiving system used the inserted known data as atraining sequence, so as to be used either for an accurate decisionvalue or for estimating an impulse response of a channel. Meanwhile,when the same known data are regularly inserted, the known data intervalmay be used as a guard interval in a channel equalizer according to thepresent invention. More specifically, since identical known data appearrepeatedly, the known data area may be used as the guard interval.Herein, the guard interval prevents interference that occurs betweenblocks due to a multiple path channel.

The above-described structure is referred to as a cyclic prefix. Thisstructure provides circular convolution to an impulse response in a timedomain between a data block transmitted from the digital broadcasttransmitting system and a channel. Accordingly, this facilitates thechannel equalizer of a digital broadcast receiving system to performchannel equalization in a frequency domain by using a fast fouriertransform (FFT) and an inverse fast fourier transform (IFFT). Morespecifically, when viewed in the frequency domain, the data blockreceived by the digital broadcast receiving system is expressed as amultiplication of the data block and the channel impulse response.Therefore, when performing the channel equalization, by multiplying theinverse of the channel in the frequency domain, the channel equalizationmay be performed more easily.

The channel equalizer according to the present invention may uses anindirect equalization method, in which the channel equalizer uses knowndata sequences, which are positioned based on a regular cycle period, inorder to estimate a channel impulse response (CIR) and to use theestimated CIR to perform the channel equalization process. Herein,indirect equalization method refers to estimating the impulse responseof a channel so as to calculate an equalization coefficient, therebyperforming the channel equalization process. Alternatively, directequalization method refers to calculating or detecting an error from achannel equalized signal so as to renew (or update) an equalizationcoefficient, thereby performing the channel equalization process.

FIG. 3 illustrates a block diagram of a channel equalizer according to afirst embodiment of the present invention. More specifically, FIG. 3illustrates a block diagram of a frequency domain channel equalizerusing an indirect equalization method according to the presentinvention. Referring to FIG. 3, the channel equalizer includes a firstfast fourier transform (FFT) unit FFT1 301, a distortion compensator302, a channel estimator 303, a second FFT unit FFT2 304, a MMSEcoefficient calculator 305, and an inverse fast fourier transform (IFFT)unit 306. Herein, any device performing complex number multiplicationmay be used as the distortion compensator 302.

In the channel equalizer having the above-described structure, as shownin FIG. 3, the first FFT unit 301 performs a FFT process on the receiveddata so as to convert the data to frequency domain data. The frequencydomain data are then outputted to the distortion compensator 302. Atthis point, if known data sequences having the same patterns areperiodically inserted in general data sequences and then transmitted,the first FFT unit 301 performs FFT on the received data by FFT blockunits, thereby converting the received data to frequency domain data.The distortion compensator 302 performs complex multiplication on theequalization coefficient calculated from the MMSE coefficient calculator305 and the frequency domain data, thereby compensating the channeldistortion of the data being outputted from the first FFT unit 301.Thereafter, the distortion-compensated data are outputted to the IFFTunit 306. The IFFT unit 306 performs inverse fast fourier transform(IFFT) on the distortion-compensated data, so as to convert thecorresponding data back to the time domain data and then outputted.

Meanwhile, the channel estimator 303 estimates the CIR by using the datareceived during the known data section and the known data of the knowndata section, wherein the known data are already known by the receivingsystem in accordance with an agreement between the receiving system andthe transmitting system. Then, the estimated CIR is outputted to thesecond FFT unit 304. For example, the channel estimator 303 estimated animpulse response of a discrete equalization channel. Herein, it isassumed that the signal being transmitted from the transmitting systemduring the known data section has passed through the discreteequalization channel. Thereafter, the estimated impulse response of thediscrete equalization channel is outputted to the second FFT unit 304.

The second FFT unit 304 performs FFT on the estimated CIR in order toconvert the estimated CIR to the frequency domain CIR. Then, the secondFFT unit 304 outputs the converted CIR to the MMSE coefficientcalculator 305. The MMSE coefficient calculator 305 uses the CIR of thefrequency domain in order to calculate the equalization coefficient andto output the calculated equalization coefficient to the distortioncompensator 302. Herein, the MMSE coefficient calculator 305 is merelyan exemplary part of the channel equalizer according to the firstembodiment of the present invention. At this point, the MMSE coefficientcalculator 305 calculates a channel equalization coefficient of thefrequency domain that can provide minimum mean square error (MMSE) fromthe estimated CIR of the frequency domain. The calculated channelequalization coefficient is outputted to the distortion compensator 302.

Meanwhile, as described above, when the input data are converted tofrequency domain data by the first FFT unit 301, the FFT block sectionshould be configured so that part of the known data of the known datasection is located both in front of and behind the general data section,as shown in FIG. 2. Thus, the influence of the channel may occur in theform of circular convolution, thereby allowing channel equalization tobe performed correctly. However, when equalization is performed by thechannel equalizer shown in FIG. 3, and when the CIR of point A and theCIR of point B (both shown in FIG. 2) are used for the equalizationprocess, the point of the general data to which the actual equalizationis applied and the point of the CIR used in the equalization process donot coincide with one another. This leads to a deficiency in theperformance of the equalizer. More specifically, this is because the CIRis the value calculated (or obtained) from the known data section, andbecause the channel equalization process of the general data section isperformed by using the CIR calculated (or obtained) from the known datasection.

In order to resolve such problems, another example of a channelequalizer is presented in FIG. 4. FIG. 4 illustrates a block diagram ofa channel equalizer of the frequency domain according to a secondembodiment of the present invention. Herein, an average value of theCIRs is used for channel equalizing the general data. More specifically,when performing the equalization process, an average value of the CIR ofpoint A and the CIR of point B is used to perform a channel equalizationprocess on the general data section between point A and point B, therebyenhancing the equalization performance. Accordingly, the channelequalizer shown in FIG. 4 further includes an average calculator 307between the channel estimator 303 and the second FFT unit 304 of FIG. 3.

More specifically, the channel estimator 303 estimates the CIR by usingthe data received during the known data section and the known data.Then, the estimated CIR is outputted to the average calculator 307.Herein, the average calculator 307 calculates an average value of theconsecutive CIRs that are being inputted and, then, outputs thecalculated average value to the second FFT unit 304. For example, theaverage value between the CIR value estimated at point A and the CIRvalue estimated at point B is calculated, so that the calculated averagevalue can be used in the channel equalization process of the generaldata located between point A and point B. Accordingly, the calculatedaverage value is outputted to the second FFT unit 304. The second FFTunit 304 converts the estimated CIR to the frequency domain CIR, whichis then outputted to the MMSE coefficient calculator 305. The MMSEcoefficient calculator 305 uses the average CIR of the frequency domainin order to calculate the equalization coefficient domain that canprovide minimum mean square error (MMSE) and to output the calculatedequalization coefficient to the distortion compensator 302. Theoperations of the components that follow are identical to those shown inFIG. 3, and so the description of the same will, therefore, be omittedfor simplicity.

FIG. 5 illustrates a block diagram of a channel equalizer according to athird embodiment of the present invention. More specifically, FIG. 5illustrates a block diagram of a frequency domain channel equalizerusing an indirect equalization method according to a third embodiment ofthe present invention. Herein, an overlap & save method is used toperform linear convolutional operation in the frequency domain.Referring to FIG. 5, the channel equalizer includes an overlap unit 401,a first fast fourier transform (FFT) unit 402, a distortion compensator403, a channel estimator 404, a second FFT unit 405, a MMSE coefficientcalculator 406, an inverse fast fourier transform (IFFT) unit 407, and asave unit 408. Herein, any device performed complex numbermultiplication may be used as the distortion compensator 403.

In the channel equalizer having the above-described structure, as shownin FIG. 5, the received data are overlapped by the overlap unit 401 andthen inputted to the first FFT unit 402. The first FFT unit 402 converts(or transforms) the overlapped data of the time domain to overlappeddata of the frequency domain by using fast fourier transform (FFT).Then, the converted data are outputted to the distortion compensator403. The distortion compensator 403 performs complex multiplication onthe equalization coefficient calculated from the MMSE coefficientcalculator 406 and the overlapped data of the frequency domain, therebycompensating the channel distortion of the overlapped data beingoutputted from the first FFT unit 402. Thereafter, thedistortion-compensated data are outputted to the IFFT unit 407. The IFFTunit 407 performs inverse fast fourier transform (IFFT) on thedistortion-compensated overlapped data, so as to convert thecorresponding data back to data (i.e., overlapped data) of the timedomain. Thereafter, the converted data are outputted to the save unit408. The save unit 408 extracts only the valid data from the overlappeddata of the time domain, thereby outputting the extracted valid data.

Meanwhile, the channel estimator 404 estimates the CIR by using the datareceived during the known data section and the known data of the knowndata section, the known data being already known by the receiving systemin accordance with an agreement between the receiving system and thetransmitting system. Then, the estimated CIR is outputted to the secondFFT unit 405. The second FFT unit 405 performs FFT on the estimated CIRof the time domain in order to convert the time domain CIR to afrequency domain CIR. Then, the second FFT unit 405 outputs theconverted CIR to the MMSE coefficient calculator 406.

The MMSE coefficient calculator 406 uses the estimated CIR of thefrequency domain, so as to calculate the equalization coefficient and tooutput the calculated equalization coefficient to the distortioncompensator 403. The MMSE coefficient calculator 406 is an exemplarypart of the channel equalizer according to the first embodiment of thepresent invention. At this point, the MMSE coefficient calculator 406calculates a channel equalization coefficient of the frequency domainthat can provide minimum mean square error (MMSE) from the estimated CIRof the frequency domain. The calculated channel equalization coefficientis outputted to the distortion compensator 403. More specifically, thefrequency domain channel equalizer of FIG. 3 performs circularconvolution calculation in the frequency domain in order to perform thechannel equalization process. On the other hand, the frequency domainchannel equalizer of FIG. 5 performs linear convolution calculation inthe frequency domain in order to perform the channel equalizationprocess. Other than this, the remaining components and the correspondingoperations are identical to one another and so, a detailed descriptionof the same will, therefore, be omitted for simplicity.

Since the frequency domain channel equalizer of FIG. 5 does not use thecharacteristics of the guard interval, unlike in FIG. 3, the channelequalizer shown in FIG. 5 is advantageous in that there are nolimitations when determining the FFT block section. More specifically,the known data do not necessarily have to be located in front of andbehind the general data which are inputted to the first FFT unit FTT1.Herein, the channel equalizers are used to estimate the CIRs by usingthe known data that are periodically transmitted. Since the CIRs areused to calculate each equalization coefficient, the speed at which theequalization coefficient is updated largely depends the cycle periodaccording to which the known data are being transmitted. Therefore, in adynamic channel (i.e., in a channel wherein the characteristics changein accordance with the time), when the channel changing speed is fasterthan the transmission cycle of the known data, the equalizationperformance may be deteriorated. At this point, when the known data arefrequently transmitted in order to compensate the channel that undergoesfrequent and fast changes, the transmission efficiency of the generaldata, in which the actual valid contents are transmitted, may bedeteriorated. Accordingly, there are limitations in reducing thetransmission cycle of the known data.

In order to resolve such problems, another example of a channelequalizer is presented in FIG. 6. FIG. 6 illustrates a block diagram ofa channel equalizer of the frequency domain according to a fourthembodiment of the present invention. Instead of frequently transmittingthe known data, the channel equalizer according to the fourth embodimentof the present invention interpolates CIRs that are estimated in theknown data section and uses the interpolated CIRs for the channelequalization of the general data. Herein, the channel equalizer of FIG.6 further includes an interpolator 409 between the channel estimator 404and the second FFT unit 405 of FIG. 5.

More specifically, the channel estimator 404 estimates the CIR by usingthe data received during the known data section and the known data.Then, the estimated CIR is outputted to the interpolator 403. Herein,the interpolator 409 uses the inputted CIR to estimate CIR of thesection that does not include the known data by using a pre-determinedinterpolation method. Then, the interpolator 409 outputs the estimatedCIR to the second FFT unit 405. The second FFT unit 405 converts theinputted CIR to the frequency domain CIR, which is then outputted to theMMSE coefficient calculator 406. The MMSE coefficient calculator 406uses the interpolated CIR of the frequency domain in order to calculatethe equalization coefficient domain that can provide minimum mean squareerror (MMSE) and to output the calculated equalization coefficient tothe distortion compensator 403. The operations of the components thatfollow are identical to those shown in FIG. 5, and so the description ofthe same will, therefore, be omitted for simplicity.

Herein, the interpolation method of the interpolator 409 corresponds toa method of estimating data of an unknown point by using the data knownfrom a particular function. The simplest example of interpolation is thelinear interpolation, which is illustrated in FIG. 7. More specifically,in a random function F(x), when given the values F(A) and F(B) each frompoints x=A and x=B, respectively, the estimated value {circumflex over(F)}(P) of the F(x) function at point x=P may be estimated by usingEquation 1 below.

$\begin{matrix}{{{\hat{F}(P)} = {{\frac{{F(B)} - {F(A)}}{B - A}\left( {P - A} \right)} + {F(A)}}}{{\hat{F}(P)} = {{\frac{B - P}{B - A}{F(A)}} + {\frac{P - A}{B - A}{F(B)}}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

If the known data sequence is periodically inserted and transmitted, thedistance between the two known data sections positioned in front of andbehind the general data section, according to the embodiment of thepresent invention, is determined as one cycle. Herein, the data sectioncorresponding to one cycle is divided into a plurality of sections. TheCIR is estimated in each divided section by using the above-describedinterpolation method. However, when one data cycle is divided into aplurality of sections, not all FFT block sections can be configured tohave the known data located (or positioned) before or behind the FFTblock section, as shown in FIG. 2. Therefore, the above-describedinterpolation method cannot be used in the frequency domain channelequalizer using the cyclic prefix. Nevertheless, when using thefrequency channel equalizer using the overlap & save method, as shown inFIG. 6.

FIG. 8 and FIG. 9 illustrate examples of overlap & save processesaccording to an embodiment of the present invention, when linearlyinterpolating the CIR. Referring to FIG. 8, data are overlapped so thatthe current FFT block and the previous FFT block are overlapped at anoverlapping ratio of 50%, and the data cycle positioned before and afterthe general data section is divided into 4 sections. In this example,the size and number of each section are decided so that a known datasequence is included in at least one section of the data cycle. This isto enable FFT block data of the section including the known datasequence directly to use the CIR estimated from the correspondingsection for the channel equalization process. Furthermore, the CIRobtained (or calculated) from corresponding section is used forinterpolating the CIR of the section that does not include any knowndata sequence.

Herein, the data inputted to the first FFT unit 402 are inserted inorder from FFT block 1 to FFT block 5, as shown in FIG. 8. The inputteddata are then inputted to the distortion compensator 403 so as to beequalized. Subsequently, the equalized data are converted to time domaindata by the IFFT unit 407. Then, only the portion corresponding to validdata is extracted from the converted by the save unit 408. Thereafter,the final data are outputted.

Referring to FIG. 8, sections 1 to 5 represent the valid data sectioncorresponding to each FFT block. At this point, since a known datasequence is included in the FFT block 1, the CIR B may be estimated.Similarly, since a known data sequence is included in the FFT block 5,the CIR C may also be estimated. In other words, the data of the FFTblock 1 use the estimated CIR B to perform channel equalization, and thedata of the FFT block 5 uses the estimated CIR C to perform channelequalization. However, since the known data sequence is not included inFFT block 2 to FFT block 4, the interpolator 409 interpolates CIR B andCIR C, thereby estimating the CIRs that may each be used in the FFTblock 2 to the FFT block 4. At this point, if linear interpolation isused, the CIRs corresponding to FFT block 2 to FFT block 4 may beestimated by using Equation 2 shown below.FFT Block 2: 0.75B+0.25CFFT Block 3: 0.5B+0.5CFFT Block 4: 0.25B+0.75C  Equation 2

Referring to FIG. 9, data are overlapped so that the current FFT blockand the previous FFT block are overlapped at an overlapping ratio of75%, and the data cycle positioned before and after the general datasection is divided into 4 sections. Similarly, in this example, the sizeand number of each section are decided so that a known data sequence isincluded in at least one section of the data cycle. Furthermore, theinterpolated and estimated CIRs are identical as those shown in FIG. 8.Yet, the only difference is that the FFT block size is twice the size ofthe FFT blocks of FIG. 8. As described above, the examples shown in FIG.8 and FIG. 9 are merely exemplary, and the degree and algorithm of theinterpolation method and the size of the FFT block may be set diverselywhenever required or necessary.

Meanwhile, as shown in FIG. 1, a sufficiently long set of known data isperiodically transmitted in the body area. Therefore, an indirectequalization method using the CIR may be adopted in the body area.However, a sufficiently long set of known data can neither betransmitted by its long size nor be transmitted periodically orconstantly in the head/tail areas. Therefore, it is not adequate toestimate the CIR by using the known data in the head/tail areas.Accordingly, a direct equalization method calculating (or obtaining)error from the output of the equalizer, thereby updating the coefficientis used in the head/tail areas.

FIG. 10 illustrates a block diagram of a channel equalizer according toa fifth embodiment of the present invention. More specifically, FIG. 10illustrates a block diagram showing the structure of a channel equalizerof a frequency domain using a direct equalization method according tothe present invention. Referring to FIG. 10, the channel equalizerincludes an overlap unit 501, a first fast fourier transform (FFT) unit502, a distortion compensator 503, an inverse fast fourier transform(IFFT) unit 504, a save unit 505, a decision unit 506, a select unit507, a subtractor 508, a zero padding unit 509, a second FFT unit 510, acoefficient update unit 511, and a delay unit 512. Herein, any devicethat performs complex number multiplication may be used as thedistortion compensator 503.

In the channel equalizer having the above-described structure, as shownin FIG. 10, the received data are overlapped by the overlap unit 501 andare outputted to the first FFT unit 502. The first FFT unit 502 performsa FFT process to convert the overlapped data of the time domain tooverlapped data of the frequency domain. Then, the converted overlappeddata are outputted to distortion compensator 503 and delay unit 512. Thedistortion compensator 503 performs complex multiplication on overlappeddata of the frequency domain and the equalization coefficient of thefrequency domain updated by the coefficient update unit 511, therebycompensating the channel distortion of the overlapped data beingoutputted from the first FFT unit 502. Thereafter, thedistortion-compensated data are outputted to the IFFT unit 504. The IFFTunit 504 performs inverse fast fourier transform (IFFT) on thedistortion-compensated overlapped data, so as to convert thecorresponding data back to data (i.e., overlapped data) of the timedomain. Then, the converted data are outputted to the save unit 505. Thesave unit 505 extracts only the valid data from the overlapped data ofthe time domain, thereby outputting the extracted valid data for datadecoding. Simultaneously, the extracted valid data are outputted to thedecision unit 506 and the subtractor 508 for updating the equalizationcoefficient.

The decision unit 506 selects one of a plurality of decision values(e.g., 8 decision values) that is most approximate to the equalized dataand outputs the selected decision value to the select unit 507. Herein,a multiplexer may be used as the select unit 507. In a general datasection, the select unit 507 selects the decision value of the decisionunit 506. Alternatively, in a known data section, the select unit 507selects the known data and outputs the selected known data to thesubtractor 508. The subtractor 508 subtracts the output of the save unit505 from the output of the select unit 507 so as to calculate (orobtain) an error value. Thereafter, the calculated error value isoutputted to the zero padding unit 509.

The zero padding unit 509 adds (or inserts) the same amount of zeros (0)corresponding to the overlapped amount of the received data in theinputted error. Then, the error extended with zeros (0) is outputted tothe second FFT unit 510. The second FFT unit 510 converts the error ofthe time domain having zeros (0) added (or inserted) therein, to theerror of the frequency domain. Thereafter, the converted error isoutputted to the coefficient update unit 511. The coefficient updateunit 511 uses the received data of the frequency domain that have beendelayed by the delay unit 512 and the error of the frequency domain soas to update the previous equalization coefficient. Thereafter, theupdated equalization coefficient is outputted to the distortioncompensator 503. At this point, the updated equalization coefficient isstored so as that it can be used as a previous equalization coefficientin a later process. In the digital broadcast transmitting system, shownin FIG. 1, data corresponding to the body area and the head/tail areasmay all be transmitted. Therefore, in order to enhance the equalizationefficiency, it is preferable to use an adequate equalizer for eachcorresponding area.

The present invention also proposes a hybrid equalization method of thechannel equalizer using both direct and indirect equalization methods.FIG. 11 illustrates a block diagram of a channel equalizer according toa sixth embodiment of the present invention. In other words, FIG. 11illustrates a block diagram showing the structure of a channel equalizerof a frequency domain by using a hybrid method according to the presentinvention. The examples presented in the sixth embodiment of the presentinvention includes a method of performing indirect channel equalizationby using a cyclic prefix on the data of the body area, and a method ofperforming direct channel equalization by using an overlap & save methodon the data of the head/tail areas.

Accordingly, referring to FIG. 11, the frequency domain channelequalizer includes a frequency domain converter 610, a distortioncompensator 620, a time domain converter 630, a first coefficientcalculating unit 640, a second coefficient calculating unit 650, and acoefficient selector 660. Herein, the frequency domain converter 610includes an overlap unit 611, a select unit 612, and a first FFT unit613. The time domain converter 630 includes an IFFT unit 631, a saveunit 632, and a select unit 633. The first coefficient calculating unit640 includes a channel estimator 641, an average calculator 642, andsecond FFT unit 643, and a MMSE coefficient calculator 644. The secondcoefficient calculating unit 650 includes a decision unit 651, a selectunit 652, a subtractor 653, a zero padding unit 654, a third FFT unit655, a coefficient updater 656, and a delay unit 657. Also, amultiplexer (MUX), which selects data that are currently being inputtedas the input data depending upon whether the data correspond to the bodyarea or to the head/tail areas, may be used as the select unit 612 ofthe frequency domain converter 610, the select unit 633 of the timedomain converter 630, and the coefficient selector 660.

In the channel equalizer having the above-described structure, as shownin FIG. 11, if the data being inputted correspond to the data of thebody area, the select unit 612 of the frequency domain converter 610selects the input data and not the output data of the overlap unit 611.In the same case, the select unit 633 of the time domain converter 630selects the output data of the IFFT unit 631 and not the output data ofthe save unit 632. The coefficient selector 660 selects the equalizationcoefficient being outputted from the first coefficient calculating unit640. Conversely, if the data being inputted correspond to the data ofthe body area, the select unit 612 of the frequency domain converter 610selects the output data of the overlap unit 611 and not the input data.In the same case, the select unit 633 of the time domain converter 630selects the output data of the save unit 632 and not the output data ofthe IFFT unit 631. The coefficient selector 660 selects the equalizationcoefficient being outputted from the second coefficient calculating unit650.

More specifically, the received data are inputted to the overlap unit611 and select unit 612 of the frequency domain converter 610, and tothe first coefficient calculating unit 640. If the inputted datacorrespond to the data of the body area, the select unit 612 selects thereceived data, which are then outputted to the first FFT unit 613. Onthe other hand, if the inputted data correspond to the data of thehead/tail areas, the select unit 612 selects the data that areoverlapped by the overlap unit 613 and are, then, outputted to the firstFFT unit 613. The first FFT unit 613 performs FFT on the time domaindata that are outputted from the select unit 612, thereby converting thetime domain data to frequency domain data. Then, the converted data areoutputted to the distortion compensator 620 and the delay unit 657 ofthe second coefficient calculating unit 650.

The distortion compensator 620 performs complex multiplication onfrequency domain data outputted from the first FFT unit 613 and theequalization coefficient outputted from the coefficient selector 660,thereby compensating the channel distortion detected in the data thatare being outputted from the first FFT unit 613. Thereafter, thedistortion-compensated data are outputted to the IFFT unit 631 of thetime domain converter 630. The IFFT unit 631 of the time domainconverter 630 performs IFFT on the channel-distortion-compensated data,thereby converting the compensated data to time domain data. Theconverted data are then outputted to the save unit 632 and the selectunit 633. If the inputted data correspond to the data of the body area,the select unit 633 selects the output data of the IFFT unit 631. On theother hand, if the inputted data correspond to the head/tail areas, theselect unit 633 selects the valid data extracted from the save unit 632.Thereafter, the selected data are outputted to be decoded and,simultaneously, outputted to the second coefficient calculating unit650.

The channel estimator 641 of the first coefficient calculating unit 640uses the data being received during the known data section and the knowndata of the known data section, the known data being already known bythe receiving system in accordance with an agreement between thereceiving system and the transmitting system, in order to estimate theCIR. Subsequently, the estimated CIR is outputted to the averagecalculator 642. The average calculator 642 calculates an average valueof the CIRs that are being inputted consecutively. Then, the calculatedaverage value is outputted to the second FFT unit 643. For example,referring to FIG. 2, the average value of the CIR value estimated atpoint A and the CIR value estimated at point B is used for the channelequalization process of the general data existing between point A andpoint B. Accordingly, the calculated average value is outputted to thesecond FFT unit 643.

The second FFT unit 643 performs FFT on the CIR of the time domain thatis being inputted, so as to convert the inputted CIR to a frequencydomain CIR. Thereafter, the converted frequency domain CIR is outputtedto the MMSE coefficient calculator 644. The MMSE coefficient calculator644 calculates a frequency domain equalization coefficient thatsatisfies the condition of using the CIR of the frequency domain so asto minimize the mean square error. The calculated equalizer coefficientof the frequency domain is then outputted to the coefficient calculator660.

The decision unit 651 of the second coefficient calculating unit 650selects one of a plurality of decision values (e.g., 8 decision values)that is most approximate to the equalized data and outputs the selecteddecision value to the select unit 652. Herein, a multiplexer may be usedas the select unit 652. In a general data section, the select unit 652selects the decision value of the decision unit 651. Alternatively, in aknown data section, the select unit 652 selects the known data andoutputs the selected known data to the subtractor 653. The subtractor653 subtracts the output of the select unit 633 included in the timedomain convertor 630 from the output of the select unit 652 so as tocalculate (or obtain) an error value. Thereafter, the calculated errorvalue is outputted to the zero padding unit 654.

The zero padding unit 654 adds (or inserts) the same amount of zeros (0)corresponding to the overlapped amount of the received data in theinputted error. Then, the error extended with zeros (0) is outputted tothe third FFT unit 655. The third FFT unit 655 converts the error of thetime domain having zeros (0) added (or inserted) therein, to the errorof the frequency domain. Thereafter, the converted error is outputted tothe coefficient update unit 656. The coefficient update unit 656 usesthe received data of the frequency domain that have been delayed by thedelay unit 657 and the error of the frequency domain so as to update theprevious equalization coefficient. Thereafter, the updated equalizationcoefficient is outputted to the distortion compensator 503. At thispoint, the updated equalization coefficient is stored so as that it canbe used as a previous equalization coefficient in a later process. Ifthe input data correspond to the data of the body area, the coefficientselector 660 selects the equalization coefficient calculated from thefirst coefficient calculating unit 640. On the other hand, if the inputdata correspond to the data of the head/tail areas, the coefficientselector 660 selects the equalization coefficient updated by the secondcoefficient calculating unit 650. Thereafter, the selected equalizationcoefficient is outputted to the distortion compensator 620.

FIG. 12 illustrates a block diagram of a channel equalizer according toa seventh embodiment of the present invention. In other words, FIG. 12illustrates a block diagram showing another example of a channelequalizer of a frequency domain by using a hybrid method according tothe present invention. In this example, a method of performing indirectchannel equalization by using an overlap & save method on the data ofthe body area, and a method of performing direct channel equalization byusing an overlap & save method on the data of the head/tail areas areillustrated.

Accordingly, referring to FIG. 12, the frequency domain channelequalizer includes a frequency domain converter 710, a distortioncompensator 720, a time domain converter 730, a first coefficientcalculating unit 740, a second coefficient calculating unit 750, and acoefficient selector 760. Herein, the frequency domain converter 710includes an overlap unit 711 and a first FFT unit 712. The time domainconverter 730 includes an IFFT unit 731 and a save unit 732. The firstcoefficient calculating unit 740 includes a channel estimator 741, aninterpolator 742, a second FFT unit 743, and a MMSE coefficientcalculator 744. The second coefficient calculating unit 750 includes adecision unit 751, a select unit 752, a subtractor 753, a zero paddingunit 754, a third FFT unit 755, a coefficient updater 756, and a delayunit 757. Also, a multiplexer (MUX), which selects data that arecurrently being inputted as the input data depending upon whether thedata correspond to the body area or to the head/tail areas, may be usedas the coefficient selector 760. More specifically, if the input datacorrespond to the data of the body area, the coefficient selector 760selects the equalization coefficient calculated from the firstcoefficient calculating unit 740. On the other hand, if the input datacorrespond to the data of the head/tail areas, the coefficient selector760 selects the equalization coefficient updated by the secondcoefficient calculating unit 750.

In the channel equalizer having the above-described structure, as shownin FIG. 12, the received data are inputted to the overlap unit 711 ofthe frequency domain converter 710 and to the first coefficientcalculating unit 740. The overlap unit 711 overlaps the input data to apre-determined overlapping ratio and outputs the overlapped data to thefirst FFT unit 712. The first FFT unit 712 performs FFT on theoverlapped time domain data, thereby converting the overlapped timedomain data to overlapped frequency domain data. Then, the converteddata are outputted to the distortion compensator 720 and the delay unit757 of the second coefficient calculating unit 750.

The distortion compensator 720 performs complex multiplication on theoverlapped frequency domain data outputted from the first FFT unit 712and the equalization coefficient outputted from the coefficient selector760, thereby compensating the channel distortion detected in theoverlapped data that are being outputted from the first FFT unit 712.Thereafter, the distortion-compensated data are outputted to the IFFTunit 731 of the time domain converter 730. The IFFT unit 731 of the timedomain converter 730 performs IFFT on the distortion-compensated data,thereby converting the compensated data to overlapped time domain data.The converted overlapped data are then outputted to the save unit 732.The save unit 732 extracts only the valid data from the overlapped timedomain data, which are then outputted for data decoding and, at the sametime, outputted to the second coefficient calculating unit 750 in orderto update the coefficient.

The channel estimator 741 of the first coefficient calculating unit 740uses the data received during the known data section and the known datain order to estimate the CIR. Subsequently, the estimated CIR isoutputted to the interpolator 742. The interpolator 742 uses theinputted CIR to estimate the CIRs (i.e., CIRs of the area that does notinclude the known data) corresponding to the points located between theestimated CIRs according to a predetermined interpolation method.Thereafter, the estimated result is outputted to the second FFT unit743. The second FFT unit 743 performs FFT on the inputted CIR, so as toconvert the inputted CIR to a frequency domain CIR. Thereafter, theconverted frequency domain CIR is outputted to the MMSE coefficientcalculator 744. The MMSE coefficient calculator 744 calculates afrequency domain equalization coefficient that satisfies the conditionof using the CIR of the frequency domain so as to minimize the meansquare error. The calculated equalizer coefficient of the frequencydomain is then outputted to the coefficient calculator 760.

The structure and operations of the second coefficient calculating unit750 is identical to those of the second coefficient calculating unit 650shown in FIG. 11. Therefore, the description of the same will be omittedfor simplicity. If the input data correspond to the data of the bodyarea, the coefficient selector 760 selects the equalization coefficientcalculated from the first coefficient calculating unit 740. On the otherhand, if the input data correspond to the data of the head/tail areas,the coefficient selector 760 selects the equalization coefficientupdated by the second coefficient calculating unit 750. Thereafter, theselected equalization coefficient is outputted to the distortioncompensator 720.

FIG. 13 illustrates an example of a demodulating unit within a digitalbroadcast receiving system having at least one of the above-describedchannel equalizers adopted therein. The demodulating unit shown in FIG.13 is merely an example given to simplify the understanding of thepresent invention. Any demodulating unit that can adopt theabove-described channel equalization method may be used in the presentinvention. Therefore, the embodiments of the present invention are notlimited to the examples set forth herein.

Referring to FIG. 13, the demodulating unit includes a demodulator 810,a channel equalizer 820, a known sequence detector 830, and an errorcorrection unit 840. Herein, the error correction unit 840 includes aViterbi decoder 841, a data deinterleaver 842, a RSdecoder/non-systematic RS parity remover 843, a derandomizer 844, a maindata packet remover 845, a packet deformatter 846, and an enhanced dataprocessor 847. More specifically, a frequency that is received through aparticular channel provides to the demodulator 810 and the knownsequence detector 830. The demodulator 810 uses the known data on thechannel frequency so as to perform carrier recovery and timing recovery,thereby create baseband signals. Thereafter, the baseband signals areoutputted to the channel equalizer 820 and the known sequence detector830.

The channel equalizer 820 uses any one of the channel equalizers shownin FIG. 3 to FIG. 6 and in FIG. 10 to FIG. 12, so as to estimate theCIR. Then, the channel equalizer 820 uses the estimated CIR tocompensate for the distortion occurring in the channel including thedemodulated signals. Thereafter, the distortion-compensated data areoutputted to the error correction unit 840. The known sequence detector830 detects the known data, which have been inserted from thetransmitting system, from the input/output data of the demodulator 810(i.e., the data prior to demodulation or the data after demodulation).Thereafter, the detected known data are outputted to the demodulator 810and the channel equalizer 820. The Viterbi decoder 841 of the errorcorrection unit 840 Viterbi-decodes the data that are outputted from thechannel equalizer 820. At this point, the 8-level decision valuesdecided by the Viterbi decoder 841 are provided to the channel equalizer820, thereby enhancing the equalizing performance. The datadeinterleaver 842 performs an inverse process of the data interleaverincluded in the transmitting system on the input data. Thereafter, thedata deinterleaver 842 outputs the deinterleaved data to the RSdecoder/non-systematic RS parity remover 843. If the received datapacket corresponds to the main data packet, the RSdecoder/non-systematic RS parity remover 843 performs a systematic RSdecoding process. Alternatively, if the received data packet correspondsto the enhanced data packet, the RS decoder/non-systematic RS parityremover 843 removes the non-systematic RS parity byte that has beeninserted in the enhanced data packet. Thereafter, the RSdecoder/non-systematic RS parity remover 843 outputs the processed datato the derandomizer 844.

The derandomizer 844 performs a derandomizing process on the output ofthe RS decoder/non-systematic RS parity remover 843. Afterwards, thederandomizer 844 inserts a MPEG synchronization byte at the beginning ofeach packet so as to output the processed data in 188-byte packet units.The output of the derandomizer 844 is outputted to the main MPEG decoder(not shown) and to the main data packet remover 845 at the same time.Meanwhile, the main data packet remover 845 removes a 188-byte unit maindata packet from the output of the derandomizer 844 and outputs theprocessed data to the packet deformatter 846. The packet deformatter 846removes the MPEG header, which was inserted to the enhanced data packetby the transmitting system, and the known data from the enhanced datapacket outputted from the main data packet remover 845. The processedenhanced data packet is then outputted to the enhanced data processor847. The enhanced data processor 847 performs null data removing,additional error correction coding, and deinterleaving processes on theoutput of the packet deformatter 846. Thus, the finally processedenhanced data are outputted.

FIG. 14 illustrates a block diagram showing the structure of a digitalbroadcast transmitting system according to an embodiment of the presentinvention. The digital broadcast (or DTV) transmitting system includes apre-processor 910, a packet multiplexer 921, a data randomizer 922, aReed-Solomon (RS) encoder/non-systematic RS encoder 923, a datainterleaver 924, a parity byte replacer 925, a non-systematic RS encoder926, a frame multiplexer 928, and a transmitting system 930. Thepre-processor 910 includes an enhanced data randomizer 911, a RS frameencoder 912, a block processor 913, a group formatter 914, a datadeinterleaver 915, and a packet formatter 916.

In the present invention having the above-described structure, main dataare inputted to the packet multiplexer 921. Enhanced data are inputtedto the enhanced data randomizer 911 of the pre-processor 910, wherein anadditional coding process is performed so that the present invention canrespond swiftly and appropriately against noise and change in channel.The enhanced data randomizer 911 randomizes the received enhanced dataand outputs the randomized enhanced data to the RS frame encoder 912. Atthis point, by having the enhanced data randomizer 911 perform therandomizing process on the enhanced data, the randomizing process on theenhanced data by the data randomizer 922 in a later process may beomitted. Either the randomizer of the conventional broadcast system maybe used as the randomizer for randomizing the enhanced data, or anyother type of randomizer may be used herein.

The RS frame encoder 912 receives the randomized enhanced data andperforms at least one of an error correction coding process and an errordetection coding process on the received data. Accordingly, by providingrobustness to the enhanced data, the data can scatter group error thatmay occur due to a change in the frequency environment. Thus, the datacan respond appropriately to the frequency environment which is verypoor and liable to change. The RS frame multiplexer 912 also includes aprocess of mixing in row units many sets of enhanced data each having apre-determined size. By performing an error correction coding process onthe inputted enhanced data, the RS frame encoder 912 adds data requiredfor the error correction and, then, performs an error detection codingprocess, thereby adding data required for the error detection process.The error correction coding uses the RS coding method, and the errordetection coding uses the cyclic redundancy check (CRC) coding method.When performing the RS coding process, parity data required for theerror correction are generated. And, when performing the CRC codingprocess, CRC data required for the error detection are generated.

The RS frame encoder 912 performs CRC coding on the RS coded enhanceddata in order to create the CRC code. The CRC code that is generated bythe CRC coding process may be used to indicate whether the enhanced datahave been damaged by an error while being transmitted through thechannel. The present invention may adopt other types of error detectioncoding methods, apart from the CRC coding method, and may also use theerror correction coding method so as to enhance the overall errorcorrection ability of the receiving system. For example, assuming thatthe size of one RS frame is 187*N bytes, that (235,187)-RS codingprocess is performed on each column within the RS frame, and that a CRCcoding process using a 2-byte (i.e., 16-bit) CRC checksum, then a RSframe having the size of 187*N bytes is expanded to a RS frame of235*(N+2) bytes. The RS frame expanded by the RS frame encoder 912 isinputted to the block processor 913. The block processor 913 codes theRS-coded and CRC-coded enhanced data at a coding rate of G/H. Then, theblock processor 913 outputs the G/H-rate coded enhanced data to thegroup formatter 914. In order to do so, the block processor 913identifies the block data bytes being inputted from the RS frame encoder912 as bits.

The block processor 913 may receive supplemental information data suchas signaling information, which include information on the system, andidentifies the supplemental information data bytes as data bits. Herein,the supplemental information data, such as the signaling information,may equally pass through the enhanced data randomizer 911 and the RSframe encoder 912 so as to be inputted to the block processor 913.Alternatively, the supplemental information data may be directlyinputted to the block processor 913 without passing through the enhanceddata randomizer 911 and the RS frame encoder 912. The signalinginformation corresponds to information required for receiving andprocessing data included in the data group in the receiving system. Suchsignaling information includes data group information, multiplexinginformation, and burst information.

As a G/H-rate encoder, the block processor 913 codes the inputted dataat a coding rate of G/H and then outputs the G/H-rate coded data. Forexample, if 1 bit of the input data is coded to 2 bits and outputted,then G is equal to 1 and H is equal to 2 (i.e., G=1 and H=2).Alternatively, if 1 bit of the input data is coded to 4 bits andoutputted, then G is equal to 1 and H is equal to 4 (i.e., G=1 and H=4).As an example of the present invention, it is assumed that the blockprocessor 913 performs a coding process at a coding rate of 1/2 (alsoreferred to as a 1/2-rate coding process) or a coding process at acoding rate of 1/4 (also referred to as a 1/4-rate coding process). Morespecifically, the block processor 913 codes the received enhanced dataand supplemental information data, such as the signaling information, ateither a coding rate of 1/2 or a coding rate of 1/4. Thereafter, thesupplemental information data, such as the signaling information, areidentified and processed as enhanced data.

Since the 1/4-rate coding process has a higher coding rate than the1/2-rate coding process, greater error correction ability may beprovided. Therefore, in a later process, by allocating the 1/4-ratecoded data in an area with deficient receiving performance within thegroup formatter 914, and by allocating the 1/2-rate coded data in anarea with excellent receiving performance, the difference in the overallperformance may be reduced. More specifically, in case of performing the1/2-rate coding process, the block processor 913 receives 1 bit andcodes the received 1 bit to 2 bits (i.e., 1 symbol). Then, the blockprocessor 913 outputs the processed 2 bits (or 1 symbol). On the otherhand, in case of performing the 1/4-rate coding process, the blockprocessor 913 receives 1 bit and codes the received 1 bit to 4 bits(i.e., 2 symbols). Then, the block processor 913 outputs the processed 4bits (or 2 symbols). Additionally, the block processor 913 performs ablock interleaving process in symbol units on the symbol-coded data.Subsequently, the block processor 913 converts to bytes the data symbolsthat are block-interleaved and have the order rearranged.

The group formatter 914 inserts the enhanced data outputted from theblock processor 913 (herein, the enhanced data may include supplementalinformation data such as signaling information including transmissioninformation) in a corresponding area within the data group, which isconfigured according to a pre-defined rule. Furthermore, in relationwith the data deinterleaving process, various types of places holders orknown data are also inserted in corresponding areas within the datagroup. At this point, the data group may be described by at least onehierarchical area. Herein, the data allocated to the each area may varydepending upon the characteristic of each hierarchical area.Additionally, each group is configured to include a fieldsynchronization signal.

The present invention shows an example of the data group being dividedinto three hierarchical areas: a head area, a body area, and a tailarea. Accordingly, in the data group that is inputted for the datadeinterleaving process, data are first inputted to the head area, theninputted to the body area, and inputted finally to the tail area. In theexample of the present invention, the head, body, and tail areas areconfigured so that the body area is not mixed with the main data areawithin the data group. Furthermore, in the present invention, the head,body, and tail areas may each be divided into lower hierarchical areas.For example, the head area may be divided into 3 lower hierarchicalareas: a far head (FH) area, a middle head (MH) area, and a near head(NH) area. The body area may be divided into 4 lower hierarchical areas:a first lower body (B1) area, a second lower body (B2) area, a thirdlower body (B3) area, and a fourth lower body (B4) area. And, finally,the tail area may be divided into 2 lower hierarchical areas: a far tail(FT) area and a near tail (NT) area.

In the example of the present invention, the group formatter 914 insertsthe enhanced data being outputted from the block processor 913 to themiddle head (MH) area, the near head (NH) area, the first to fourthlower body (B1 to B4) areas, and the near tail (NT) area. Herein, thetype of enhanced data may vary depending upon the characteristic of eacharea. The data group is divided into a plurality of areas so that eacharea may be used for different purposes. More specifically, areas havingless interference with the main data may show more enhanced receivingperformance as compared with area having more interference with the maindata. Additionally, when using the system in which the known data areinserted in the data group and then transmitted, and when a long set ofconsecutive known data is to be periodically (or regularly) inserted inthe enhanced data, the body area is capable of regularly receiving suchenhanced data having a predetermined length. However, since the enhanceddata may be mixed with the main data in the head and tail areas, it isdifficult to regularly insert the known data in these areas, and it isalso difficult to insert long known data sets that are consecutive inthese areas.

Details such as the size of the data group, the number of hierarchicalareas within the data group and the size of each hierarchical area, andthe number of enhanced data bytes that may be inserted in eachhierarchical area may vary depending upon the design of the systemdesigner. Therefore, the above-described embodiment is merely an examplethat can facilitate the description of the present invention. In thegroup formatter 914, the data group may be configured to include aposition (or place) in which the field synchronization signal is to beinserted. When assuming that the data group is divided into a pluralityof hierarchical areas as described above, the block processor 913 maycode the data that are to be inserted in each area at different codingrates.

In the present invention, based upon the areas that are each expected toshow different performance after the equalization process when using thechannel information that may be used for the channel equalizationprocess in the receiving system, a different coding rate may be appliedto each of these areas. For example, the block processor 913 codes theenhanced data that are to be inserted in the near head (NH) area and thefirst to fourth lower body (B1 to B4) areas at a 1/2-coding rate.Thereafter, the group formatter 914 may insert the 1/2-rate codedenhanced data in the near head (NH) area and the first to fourth lowerbody (B1 to B4) areas. On the other hand, the block processor 913 codesthe enhanced data that are to be inserted in the middle head (MH) areaand the near tail (NT) area at a 1/4-coding rate, which has greatererror correction ability than the 1/2-coding rate. Subsequently, thegroup formatter 914 may insert the 1/2-rate coded enhanced data in themiddle head (MH) area and the near tail (NT) area. Furthermore, theblock processor 913 codes the enhanced data that are to be inserted inthe far head (FH) area and the far tail (FT) area at a coding ratehaving even greater error correction ability than the 1/4-coding rate.Thereafter, the group formatter 914 may inserts the coded enhanced dataeither in the far head (FH) and far tail (FT) areas or in a reservedarea for future usage.

Apart from the enhanced data, the group formatter 913 may also insertsupplemental information data such as signaling information indicatingthe overall transmission information in the data group. Also, apart fromthe coded enhanced data outputted from the block processor 913, and inrelation with the data deinterleaving process in a later process, thegroup formatter 914 may also insert a MPEG header place holder, anon-systematic RS parity place holder, and a main data place holder inthe data group. Herein, the main data group place holder is insertedbecause the enhanced data and the main data may be mixed in the head andtail areas depending upon the input of the data deinterleaver. Forexample, based upon the output of the data after being deinterleaved,the place holder for the MPEG header may be allocated to the front ofeach data packet. Additionally, the group formatter 914 may eitherinsert known data generated according to a pre-defined rule, or insert aknown data place holder for inserting known data in a later process.Furthermore, a place holder for the initialization of the trellisencoder module 927 is inserted in a corresponding area. For example, theinitialization data place holder may be inserted at the beginning (orfront) of the data place sequence.

The output of the group formatter 914 is inputted to the datadeinterleaver 915. And, the data deinterleaver 915 performs an inverseprocess of the data interleaver deinterleaving the data and place holderwithin the data group being outputted from the group formatter 914.Thereafter, the data deinterleaver 915 outputs the deinterleaved data tothe packet formatter 916. Among the data deinterleaved and inputted, thepacket formatter 916 removes the main data place holder and RS parityplace holder that were allocated for the deinterleaving process from theinputted deinterleaved data. Thereafter, the remaining portion of thecorresponding data is grouped, and 4 bytes of MPEG header are insertedtherein. The 4-byte MPEG header is configured of a 1-byte MPEGsynchronization byte added to the 3-byte MPEG header place holder.

When the group formatter 914 inserts the known data place holder, thepacket formatter 916 may either insert actual known data in the knowndata place holder or output the known data place holder without anychange or modification for a replacement insertion in a later process.Afterwards, the packet formatter 916 divides the data within theabove-described packet-formatted data group into 188-byte unit enhanceddata packets (i.e., MPEG TS packets), which are then provided to thepacket multiplexer 921. The packet multiplexer 921 multiplexes the188-byte unit enhanced data packet and main data packet outputted fromthe packet formatter 916 according to a pre-defined multiplexing method.Subsequently, the multiplexed data packets are outputted to the datarandomizer 922. The multiplexing method may be modified or altered inaccordance with diverse variables of the system design.

As an example of the multiplexing method of the packet multiplexer 921,the enhanced data burst section and the main data section may beidentified along a time axis (or a chronological axis) and may bealternately repeated. At this point, the enhanced data burst section maytransmit at least one data group, and the main data section may transmitonly the main data. The enhanced data burst section may also transmitthe main data. If the enhanced data are outputted in a burst structure,as described above, the receiving system receiving only the enhanceddata may turn the power on only during the burst section so as toreceive the enhanced data, and may turn the power off during the maindata section in which main data are transmitted, so as to prevent themain data from being received, thereby reducing the power consumption ofthe receiving system.

When the data being inputted correspond to the main data packet, thedata randomizer 922 performs the same randomizing process of theconventional randomizer. More specifically, the MPEG synchronizationbyte included in the main data packet is discarded and a pseudo randombyte generated from the remaining 187 bytes is used so as to randomizethe data. Thereafter, the randomized data are outputted to the RSencoder/non-systematic RS encoder 923. However, when the inputted datacorrespond to the enhanced data packet, the MPEG synchronization byte ofthe 4-byte MPEG header included in the enhanced data packet isdiscarded, and data randomizing is performed only on the remaining3-byte MPEG header. Randomizing is not performed on the remainingportion of the enhanced data. Instead, the remaining portion of theenhanced data is outputted to the RS encoder/non-systematic RS encoder923. This is because the randomizing process has already been performedon the enhanced data by the enhanced data randomizer 911 in an earlierprocess. Herein, a data randomizing process may or may not be performedon the known data (or known data place holder) and the initializationdata place holder included in the enhanced data packet.

The RS encoder/non-systematic RS encoder 923 RS-codes the datarandomized by the data randomizer 922 or the data bypassing the datarandomizer 922. Then, the RS encoder/non-systematic RS encoder 923 addsa 20-byte RS parity to the coded data, thereby outputting theRS-parity-added data to the data interleaver 924. At this point, if theinputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 923 performs a systematic RS-codingprocess identical to that of the conventional receiving system on theinputted data, thereby adding the 20-byte RS parity at the end of the187-byte data. Alternatively, if the inputted data correspond to theenhanced data packet, the 20 bytes of RS parity gained by performing thenon-systematic RS-coding are respectively inserted in the decided paritybyte places within the enhanced data packet. Herein, the datainterleaver 924 corresponds to a byte unit convolutional interleaver.The output of the data interleaver 924 is inputted to the parity bytereplacer 925 and the non-systematic RS encoder 926.

Meanwhile, a memory within the trellis encoding module 927, which ispositioned after the parity byte replacer 925, should first beinitialized in order to allow the output data of the trellis encodingmodule 927 so as to become the known data defined based upon anagreement between the receiving system and the transmitting system. Morespecifically, the memory of the trellis encoding module 927 should firstbe initialized before the known data sequence being inputted istrellis-encoded. At this point, the beginning of the known data sequencethat is inputted corresponds to the initialization data place holderinserted by the group formatter 914 and not the actual known data.Therefore, a process of generating initialization data right before thetrellis-encoding of the known data sequence being inputted and a processof replacing the initialization data place holder of the correspondingtrellis encoding module memory with the newly generated initializationdata are required.

A value of the trellis memory initialization data is decided based uponthe memory status of the trellis encoding module 927, thereby generatingthe trellis memory initialization data accordingly. Due to the influenceof the replace initialization data, a process of recalculating the RSparity, thereby replacing the RS parity outputted from the trellisencoding module 927 with the newly calculated RS parity is required.Accordingly, the non-systematic RS encoder 926 receives the enhanceddata packet including the initialization data place holder that is to bereplaced with the initialization data from the data interleaver 924 andalso receives the initialization data from the trellis encoding module927. Thereafter, among the received enhanced data packet, theinitialization data place holder is replaced with the initializationdata. Subsequently, the RS parity data added to the enhanced data packetis removed. Then, a new non-systematic RS parity is calculated andoutputted to the parity byte replacer 925. Accordingly, the parity bytereplacer 925 selects the output of the data interleaver 924 as the datawithin the enhanced data packet, and selects the output of thenon-systematic RS encoder 926 as the RS parity. Thereafter, the paritybyte replacer 925 outputs the selected data.

Meanwhile, if the main data packet is inputted, or if the enhanced datapacket that does not include the initialization data place holder thatis to be replaced, the parity byte replacer 925 selects the data and RSparity outputted from the data interleaver 924 and directly outputs theselected data to the trellis encoding module 927 without modification.The trellis encoding module 927 converts the byte-unit data tosymbol-unit data and 12-way interleaves and trellis-encodes theconverted data, which are then outputted to the frame multiplexer 928.The frame multiplexer 928 inserts field synchronization and segmentsynchronization signals in the output of the trellis encoding module 927and then outputs the processed data to the transmitter 930. Herein, thetransmitter 930 includes a pilot inserter 931, a modulator 932, and aradio frequency (RF) up-converter 933. The operation of the transmitter930 is identical to the conventional transmitters. Therefore, a detaileddescription of the same will be omitted for simplicity.

FIG. 15 illustrates a block diagram of a demodulating unit included inthe receiving system according to another embodiment of the presentinvention. Herein, the demodulating unit may effectively process signalstransmitted from the transmitting system shown in FIG. 14. Referring toFIG. 15, the demodulating unit includes a demodulator 1001, a channelequalizer 1002, a known data detector 1003, a block decoder 1004, anenhanced data deformatter 1005, a RS frame decoder 1006, an enhanceddata derandomizer 1007, a data deinterleaver 1008, a RS decoder 1009,and a main data derandomizer 1010. For simplicity, the demodulator 1001,the channel equalizer 1002, the known data detector 1003, the blockdecoder 1004, the enhanced data deformatter 1005, the RS frame decoder1006, and the enhanced data derandomizer 1007 will be referred to as anenhanced data processor. And, the data deinterleaver 1008, the RSdecoder 1009, and the main data derandomizer 1010 will be referred to asa main data processor.

More specifically, the enhanced data including known data and the maindata are received through the tuner and inputted to the demodulator 1001and the known data detector 1003. The demodulator 1001 performsautomatic gain control, carrier wave recovery, and timing recovery onthe data that are being inputted, thereby creating baseband data, whichare then outputted to the equalizer 1002 and the known data detector1003. The equalizer 1002 compensates the distortion within the channelincluded in the demodulated data. Then, the equalizer 1002 outputs thecompensated data to the block decoder 1004.

At this point, the known data detector 1003 detects the known data placeinserted by the transmitting system to the input/output data of thedemodulator 1001 (i.e., data prior to demodulation or data afterdemodulation). Then, along with the position information, the known datadetector 1003 outputs the symbol sequence of the known data generatedfrom the corresponding position to the demodulator 1001 and theequalizer 1002. Additionally, the known data detector 1003 outputsinformation enabling the block decoder 1004 to identify the enhanceddata being additionally encoded by the transmitting system and the maindata that are not additionally encoded to the block decoder 1004.Furthermore, although the connection is not shown in FIG. 15, theinformation detected by the known data detector 1003 may be used in theoverall receiving system and may also be used in the enhanced dataformatter 1005 and the RS frame decoder 1006.

By using the known data symbol sequence when performing the timingrecovery or carrier wave recovery, the demodulating performance of thedemodulator 1001 may be enhanced. Similarly, by using the known data,the channel equalizing performance of the channel equalizer 1002 may beenhanced. Furthermore, by feeding-back the demodulation result of theblock demodulator 1004, the channel equalizing performance may also beenhanced. Herein, the channel equalizer 1002 may perform channelequalization through various methods. In the present invention, a methodof estimating a channel impulse response (CIR) for performing thechannel equalization process will be given as an example of the presentinvention. More specifically, in the present invention, the channelimpulse response (CIR) is differently estimated and applied inaccordance with each hierarchical area within the data group that aretransmitted from the transmitting system. Furthermore, by using theknown data having the position (or place) and contents pre-knownaccording to an agreement between the transmitting system and thereceiving system, so as to estimate the CIR, the channel equalizationprocess may be processed with more stability.

In the present invention, one data group that is inputted for channelequalization is divided into three hierarchical areas: a head area, abody area, and a tail area. Then, each of the areas is divided intolower hierarchical areas. More specifically, the head area may bedivided into a far head (FH) area, a middle head (MH) area, and a nearhead (NH) area. And, the tail area may be divided into a far tail (FT)area and a near tail (NT) area. Furthermore, based upon a long knowndata sequence, the body area may be divided into 4 lower hierarchicalareas: a first lower body (B1) area, a second lower body (B2) area, athird lower body (B3) area, and a fourth lower body (B4) area. Inperforming channel equalization on the data within the data group byusing the CIR estimated from the field synchronization signal and theknown data sequence, and in accordance with the characteristic of eacharea, either one of the estimated CIRs may be directly used withoutmodification, or a CIR created by interpolating or extrapolating aplurality of CIRs may be used.

Meanwhile, if the data being channel equalized and then inputted to theblock decoder 1004 correspond to the enhanced data on which additionalencoding and trellis encoding are both performed by the transmittingsystem, trellis-decoding and additional decoding processes are performedas inverse processes of the transmitting system. Alternatively, if thedata being channel equalized and then inputted to the block decoder 1004correspond to the main data on which additional encoding is notperformed and only trellis-encoding is performed by the transmittingsystem, only the trellis-decoding process is performed. The data groupdecoded by the block decoder 1004 is inputted to the enhanced datadeformatter 1005, and the main data packet is inputted to the datadeinterleaver 1008.

More specifically, if the inputted data correspond to the main data, theblock decoder 1004 performs Viterbi decoding on the inputted data, so asto either output a hard decision value or hard-decide a soft decisionvalue and output the hard-decided result. On the other hand, if theinputted correspond to the enhanced data, the block decoder 1004 outputseither a hard decision value or a soft decision value on the inputtedenhanced data. In other words, if the data inputted to the block decoder1004 correspond to the enhanced data, the block decoder 1004 performs adecoding process on the data encoded by the block processor and thetrellis encoder of the transmitting system. At this point, the output ofthe RS frame encoder included in the pre-processor of the transmittingsystem becomes an external code, and the output of the block processorand the trellis encoder becomes an internal code. In order to showmaximum performance of the external code when decoding such connectioncodes, the decoder of the internal code should output a soft decisionvalue. Therefore, the block decoder 1004 may output a hard decisionvalue on the enhanced data. However, when required, it is morepreferable that the block decoder 1004 outputs a soft decision value.

The present invention may also be used for configuring a reliability mapusing the soft decision value. The reliability map determines andindicates whether a byte corresponding to a group of 8 bits decided bythe code of the soft decision value is reliable. For example, when anabsolute value of the soft decision value exceeds a pre-determinedthreshold value, the value of the bit corresponding to the soft decisionvalue code is determined to be reliable. However, if the absolute valuedoes not exceed the pre-determined threshold value, then the value ofthe corresponding bit is determined to be not reliable. Further, if atleast one bit among the group of 8 bits, which are determined based uponthe soft decision value, is determined to be not reliable, then thereliability map indicates that the entire byte is not reliable. Herein,the process of determining the reliability by 1-bit units is merelyexemplary. The corresponding byte may also be indicated to be notreliable if a plurality of bits (e.g., 4 bits) is determined to be notreliable.

Conversely, when all of the bits are determined to be reliable withinone byte (i.e., when the absolute value of the soft value of all bitsexceeds the pre-determined threshold value), then the reliability mapdetermines and indicates that the corresponding data byte is reliable.Similarly, when more than 4 bits are determined to be reliable withinone data byte, then the reliability map determines and indicates thatthe corresponding data byte is reliable. The estimated numbers aremerely exemplary and do not limit the scope and spirit of the presentinvention. Herein, the reliability map may be used when performing errorcorrection decoding processes.

Meanwhile, the data deinterleaver 1008, the RS decoder 1009, and themain data derandomizer 1010 are blocks required for receiving the maindata. These blocks may not be required in a receiving system structurethat receives only the enhanced data. The data deinterleaver 1008performs an inverse process of the data interleaver of the transmittingsystem. More specifically, the data deinterleaver 1008 deinterleaves themain data being outputted from the block decode 1004 and outputs thedeinterleaved data to the RS decoder 1009. The RS decoder 1009 performssystematic RS decoding on the deinterleaved data and outputs thesystematically decoded data to the main data derandomizer 1010. The maindata derandomizer 1010 receives the data outputted from the RS decoder1009 so as to generate the same pseudo random byte as that of therandomizer in the transmitting system. The main data derandomizer 1010then performs a bitwise exclusive OR (XOR) operation on the generatedpseudo random data byte, thereby inserting the MPEG synchronizationbytes to the beginning of each packet so as to output the data in188-byte main data packet units.

Herein, the format of the data being outputted to the enhanced datadeformatter 1005 from the block decoder 1004 is a data group format. Atthis point, the enhanced data deformatter 1005 already knows thestructure of the input data. Therefore, the enhanced data deformatter1005 identifies the system information including signaling informationand the enhanced data from the data group. Thereafter, the identifiedsignaling information is transmitted to where the system information isrequired, and the enhanced data are outputted to the RS frame decoder1006. The enhanced data deformatter 1005 removes the known data, trellisinitialization data, and MPEG header that were included in the main dataand the data group and also removes the RS parity that was added by theRS encoder/non-systematic RS encoder of the transmitting system.Thereafter, the processed data are outputted to the RS frame decoder1006.

More specifically, the RS frame decoder 1006 receives the RS-coded andCRC-coded enhanced data from the enhanced data deformatter 1005 so as toconfigure the RS frame. The RS frame decoder 1006 performs an inverseprocess of the RS frame encoder included in the transmitting system,thereby correcting the errors within the RS frame. Then, the 1-byte MPEGsynchronization byte, which was removed during the RS frame codingprocess, is added to the error corrected enhanced data packet.Subsequently, the processed data are outputted to the enhanced dataderandomizer 1007. Herein, the enhanced data derandomizer 1007 performsa derandomizing process, which corresponds to an inverse process of theenhanced data randomizer included in the transmitting system, on thereceived enhanced data. Then, by outputting the processed data, theenhanced data transmitted from the transmitting system can be obtained.

According to an embodiment of the present invention, the RS framedecoder 1006 may also be configured as follows. The RS frame decoder1006 may perform a CRC syndrome check on the RS frame, thereby verifyingwhether or not an error has occurred in each row. Subsequently, the CRCchecksum is removed and the presence of an error is indicated on a CRCerror flag corresponding to each row. Then, a RS decoding process isperformed on the RS frame having the CRC checksum removed in a columndirection. At this point, depending upon the number of CRC error flags,a RS erasure decoding process may be performed. More specifically, bychecking the CRC error flags corresponding to each row within the RSframe, the number of CRC error flags may be determined whether it isgreater or smaller than the maximum number of errors, when RS decodingthe number of rows with errors (or erroneous rows) in the columndirection. Herein, the maximum number of errors corresponds to thenumber of parity bytes inserted during the RS decoding process. As anexample of the present invention, it is assumed that 48 parity bytes areadded to each column.

If the number of rows with CRC errors is equal to or smaller than themaximum number of errors (e.g., 48), which may be corrected by the RSerasure decoding process, the RS erasure decoding process is performedon the RS frame in the column direction. Thereafter, the 48 bytes ofparity data that were added at the end of each column are removed.However, if the number of rows with CRC errors is greater than themaximum number of errors (e.g., 48), which may be corrected by the RSerasure decoding process, the RS erasure decoding process cannot beperformed. In this case, the error may be corrected by performing ageneral RS decoding process.

As another embodiment of the present invention, the error correctionability may be enhanced by using the reliability map created whenconfiguring the RS frame from the soft decision value. Morespecifically, the RS frame decoder 1006 compares the absolute value ofthe soft decision value obtained from the block decoder 1004 to thepre-determined threshold value so as to determine the reliability of thebit values that are decided by the code of the corresponding softdecision value. Then, 8 bits are grouped to configure a byte. Then, thereliability information of the corresponding byte is indicated on thereliability map. Therefore, even if a specific row is determined to haveCRC errors as a result of the CRC syndrome checking process of thecorresponding row, it is not assumed that all of the data bytes includedin the corresponding row have error. Instead, only the data bytes thatare determined to be not reliable, after referring to the reliabilityinformation on the reliability map, are set to have errors. In otherwords, regardless of the presence of CRC errors in the correspondingrow, only the data bytes that are determined to be not reliable (orunreliable) by the reliability map are set as erasure points.

Thereafter, if the number of erasure points for each column is equal toor smaller than the maximum number of errors (e.g., 48), the RS erasuredecoding process is performed on the corresponding the column.Conversely, if the number of erasure points is greater than the maximumnumber of errors (e.g., 48), which may be corrected by the RS erasuredecoding process, a general decoding process is performed on thecorresponding column. In other words, if the number of rows having CRCerrors is greater than the maximum number of errors (e.g., 48), whichmay be corrected by the RS erasure decoding process, either a RS erasuredecoding process or a general RS decoding process is performed on aparticular column in accordance with the number of erasure point withinthe corresponding column, wherein the number is decided based upon thereliability information on the reliability map. When the above-describedprocess is performed, the error correction decoding process is performedin the direction of all of the columns included in the RS frame.Thereafter, the 48 bytes of parity data added to the end of each columnare removed.

FIG. 16 illustrates a block diagram showing the structure of a digitalbroadcast receiving system according to an embodiment of the presentinvention. Referring to FIG. 16, the digital broadcast receiving systemincludes a tuner 2001, a demodulating unit 2002, a demultiplexer 2003,an audio decoder 2004, a video decoder 2005, a native TV applicationmanager 2006, a channel manager 2007, a channel map 2008, a first memory2009, a data decoder 2010, a second memory 2011, a system manager 2012,a data broadcasting application manager 2013, a storage controller 2014,and a third memory 2015. Herein, the third memory 2015 is a mass storagedevice, such as a hard disk drive (HDD) or a memory chip. The tuner 2001tunes a frequency of a specific channel through any one of an antenna,cable, and satellite. Then, the tuner 2001 down-converts the tunedfrequency to an intermediate frequency (IF), which is then outputted tothe demodulating unit 2002. At this point, the tuner 2001 is controlledby the channel manager 2007. Additionally, the result and strength ofthe broadcast signal of the tuned channel are also reported to thechannel manager 2007. The data that are being received by the frequencyof the tuned specific channel include main data, enhanced data, andtable data for decoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data.For example, the meta data use the XML application so as to betransmitted through a DSM-CC protocol.

The demodulating unit 2002 performs demodulation and channelequalization on the signal being outputted from the tuner 2001, therebyidentifying the main data and the enhanced data. Thereafter, theidentified main data and enhanced data are outputted in TS packet units.Examples of the demodulating unit 2002 are shown in FIG. 13 and FIG. 15.The demodulating unit shown in FIG. 13 and FIG. 15 is merely exemplaryand the scope of the present invention is not limited to the examplesset forth herein. In the embodiment given as an example of the presentinvention, only the enhanced data packet outputted from the demodulatingunit 2002 is inputted to the demultiplexer 2003. In this case, the maindata packet is inputted to another demultiplexer (not shown) thatprocesses main data packets. Herein, the storage controller 2014 is alsoconnected to the other demultiplexer in order to store the main dataafter processing the main data packets. The demultiplexer of the presentinvention may also be designed to process both enhanced data packets andmain data packets in a single demultiplexer.

The storage controller 2014 is interfaced with the demultiplexer so asto control instant recording, reserved (or pre-programmed) recording,time shift, and so on of the enhanced data and/or main data. Forexample, when one of instant recording, reserved (or pre-programmed)recording, and time shift is set and programmed in the receiving system(or receiver) shown in FIG. 16, the corresponding enhanced data and/ormain data that are inputted to the demultiplexer are stored in the thirdmemory 2015 in accordance with the control of the storage controller2014. The third memory 2015 may be described as a temporary storage areaand/or a permanent storage area. Herein, the temporary storage area isused for the time shifting function, and the permanent storage area isused for a permanent storage of data according to the user's choice (ordecision).

When the data stored in the third memory 2015 need to be reproduced (orplayed), the storage controller 2014 reads the corresponding data storedin the third memory 2015 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 2003 shown in FIG. 16). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 2015 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 2015 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 2015 pass troughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 2014 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 2015 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 2014compression encodes the inputted data and stored the compression-encodeddata to the third memory 2015. In order to do so, the storage controller2014 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 2014.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 2015, the storage controller2014 scrambles the input data and stores the scrambled data in the thirdmemory 2015. Accordingly, the storage controller 2014 may include ascramble algorithm for scrambling the data stored in the third memory2015 and a descramble algorithm for descrambling the data read from thethird memory 2015. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 2003 receives the real-time data outputtedfrom the demodulating unit 2002 or the data read from the third memory2015 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 2003 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 2003 and the subsequent elements.

The demultiplexer 2003 demultiplexes enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 2010. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 2010 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The EIT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section”, and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PISP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number). The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (EIT), and a time and data table (TDT). TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NIT includes all tuning informationthat is used during the IRD set-up. The NIT may be used for informing ornotifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The EIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0x95’ is assigned as the value of a stream_typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream_type field value is‘0x95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 2010, thedemultiplexer 2003 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 2010. The demultiplexer 2003 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 2010by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 2003 performs the section filtering process by referringto a table_id field, a version_number field, a section_number field,etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PID must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer2003 may output only an application information table (AIT) to the datadecoder 2010 by section filtering. The AIT includes information on anapplication being operated in the receiving system for the data service.The AIT may also be referred to as an XAIT, and an AMT. Therefore, anytable including application information may correspond to the followingdescription. When the AIT is transmitted, a value of ‘0x05’ may beassigned to a stream_type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 2011 by the data decoder 2010.

The data decoder 2010 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 2011.The data decoder 2010 groups a plurality of sections having the sametable identification (table_id) so as to configure a table, which isthen parsed. Thereafter, the parsed result is stored as a database inthe second memory 2011. At this point, by parsing data and/or sections,the data decoder 2010 reads all of the remaining actual section datathat are not section-filtered by the demultiplexer 2003. Then, the datadecoder 2010 stores the read data to the second memory 2011. The secondmemory 2011 corresponds to a table and data carousel database storingsystem information parsed from tables and enhanced data parsed from theDSM-CC section. Herein, a table_id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT.

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 2011 or be outputted to thedata broadcasting application manager 2013. In addition, reference maybe made to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 2010 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 2007.

The channel manager 2007 may refer to the channel map 2008 in order totransmit a request for receiving system-related information data to thedata decoder 2010, thereby receiving the corresponding result. Inaddition, the channel manager 2007 may also control the channel tuningof the tuner 2001. Furthermore, the channel manager 2007 may directlycontrol the demultiplexer 2003, so as to set up the A/V PID, therebycontrolling the audio decoder 2004 and the video decoder 2005. The audiodecoder 2004 and the video decoder 2005 may respectively decode andoutput the audio data and video data demultiplexed from the main datapacket. Alternatively, the audio decoder 2004 and the video decoder 2005may respectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 2003 are respectively decoded by the audio decoder2004 and the video decoder 2005. For example, an audio-coding (AC)-3decoding algorithm may be applied to the audio decoder 2004, and aMPEG-2 decoding algorithm may be applied to the video decoder 2005.

Meanwhile, the native TV application manager 2006 operates a nativeapplication program stored in the first memory 2009, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 2006 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 2006 and the databroadcasting application manager 2013. Furthermore, the native TVapplication manager 2006 controls the channel manager 2007, therebycontrolling channel-associated, such as the management of the channelmap 2008, and controlling the data decoder 2010. The native TVapplication manager 2006 also controls the GUI of the overall receivingsystem, thereby storing the user request and status of the receivingsystem in the first memory 2009 and restoring the stored information.

The channel manager 2007 controls the tuner 2001 and the data decoder2010, so as to managing the channel map 2008 so that it can respond tothe channel request made by the user. More specifically, channel manager2007 sends a request to the data decoder 2010 so that the tablesassociated with the channels that are to be tuned are parsed. Theresults of the parsed tables are reported to the channel manager 2007 bythe data decoder 2010. Thereafter, based on the parsed results, thechannel manager 2007 updates the channel map 2008 and sets up a PID inthe demultiplexer 2003 for demultiplexing the tables associated with thedata service data from the enhanced data.

The system manager 2012 controls the booting of the receiving system byturning the power on or off. Then, the system manager 2012 stores ROMimages (including downloaded software images) in the first memory 2009.More specifically, the first memory 2009 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 2011 so as to provide the user with the dataservice. If the data service data are stored in the second memory 2011,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 2009 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory2009 upon the shipping of the receiving system, or be stored in thefirst 2009 after being downloaded. The application program for the dataservice (i.e., the data service providing application program) stored inthe first memory 2009 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 2013 operates thecorresponding application program stored in the first memory 2009 so asto process the requested data, thereby providing the user with therequested data service. And, in order to provide such data service, thedata broadcasting application manager 2013 supports the graphic userinterface (GUI). Herein, the data service may be provided in the form oftext (or short message service (SMS)), voice message, still image, andmoving image. The data broadcasting application manager 2013 may beprovided with a platform for executing the application program stored inthe first memory 2009. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 2013 executing the data serviceproviding application program stored in the first memory 2009, so as toprocess the data service data stored in the second memory 2011, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiving system that is not equipped with anelectronic map and/or a GPS system in the form of at least one of a text(or short message service (SMS)), a voice message, a graphic message, astill image, and a moving image. In this case, is a GPS module ismounted on the receiving system shown in FIG. 16, the GPS modulereceives satellite signals transmitted from a plurality of low earthorbit satellites and extracts the current position (or location)information (e.g., longitude, latitude, altitude), thereby outputtingthe extracted information to the data broadcasting application manager2013.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 2011, the first memory 2009, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 2013, the dataservice data stored in the second memory 2011 are read and inputted tothe data broadcasting application manager 2013. The data broadcastingapplication manager 2013 translates (or deciphers) the data service dataread from the second memory 2011, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 17 illustrates a block diagram showing the structure of a digitalbroadcast (or television) receiving system according to anotherembodiment of the present invention. Referring to FIG. 17, the digitalbroadcast receiving system includes a tuner 3001, a demodulating unit3002, a demultiplexer 3003, a first descrambler 3004, an audio decoder3005, a video decoder 3006, a second descrambler 3007, an authenticationunit 3008, a native TV application manager 3009, a channel manager 3010,a channel map 3011, a first memory 3012, a data decoder 3013, a secondmemory 3014, a system manager 3015, a data broadcasting applicationmanager 3016, a storage controller 3017, a third memory 3018, and atelecommunication module 3019. Herein, the third memory 3018 is a massstorage device, such as a hard disk drive (HDD) or a memory chip. Also,during the description of the digital broadcast (or television or DTV)receiving system shown in FIG. 17, the components that are identical tothose of the digital broadcast receiving system of FIG. 16 will beomitted for simplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descramble the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating (or verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 3004 and 3007, and the authentication means will bereferred to as an authentication unit 3008. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.17 illustrates an example of the descramblers 3004 and 3007 and theauthentication unit 3008 being provided inside the receiving system,each of the descramblers 3004 and 3007 and the authentication unit 3008may also be separately provided in an internal or external module.Herein, the module may include a slot type, such as a SD or CF memory, amemory stick type, a USB type, and so on, and may be detachably fixed tothe receiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 3008, the scrambled broadcastingcontents are descrambled by the descramblers 3004 and 3007, therebybeing provided to the user. At this point, a variety of theauthentication method and descrambling method may be used herein.However, an agreement on each corresponding method should be madebetween the receiving system and the transmitting system. Hereinafter,the authentication and descrambling methods will now be described, andthe description of identical components or process steps will be omittedfor simplicity.

The receiving system including the authentication unit 3008 and thedescramblers 3004 and 3007 will now be described in detail. Thereceiving system receives the scrambled broadcasting contents throughthe tuner 3001 and the demodulating unit 3002. Then, the system manager3015 decides whether the received broadcasting contents have beenscrambled. Herein, the demodulating unit 3002 may be included as ademodulating means according to embodiments of the present invention asdescribed in FIG. 13 and FIG. 15. However, the present invention is notlimited to the examples given in the description set forth herein. Ifthe system manager 3015 decides that the received broadcasting contentshave been scrambled, then the system manager 3015 controls the system tooperate the authentication unit 3008. As described above, theauthentication unit 3008 performs an authentication process in order todecide whether the receiving system according to the present inventioncorresponds to a legitimate host entitled to receive the paidbroadcasting service. Herein, the authentication process may vary inaccordance with the authentication methods.

For example, the authentication unit 3008 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 3008 may extract the IP address from thedecapsulated IP datagram, thereby obtaining the receiving systeminformation that is mapped with the IP address. At this point, thereceiving system should be provided, in advance, with information (e.g.,a table format) that can map the IP address and the receiving systeminformation. Accordingly, the authentication unit 3008 performs theauthentication process by determining the conformity between the addressof the corresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 3008 determines that the two types ofinformation conform to one another, then the authentication unit 3008determines that the receiving system is entitled to receive thecorresponding broadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or antherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with a receivingsystem-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit 3008 of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 3008determines whether the identification information conform to each other,so as to perform the authentication process. More specifically, if theauthentication unit 3008 determines that the information conform to eachother, then the authentication unit 3008 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 3008 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 3015 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 3015 transmits thepayment information to the remote transmitting system through thetelecommunication module 3019.

The authentication unit 3008 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 3008 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 3008 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 3008, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 3004 and 3007. Herein,the first and second descramblers 3004 and 3007 may be included in aninternal module or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 3004 and 3007, so as to perform the descrambling process.More specifically, the first and second descramblers 3004 and 3007 maybe included in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 3004 and 3007may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 3004 and 3007 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 3004 and 3007 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 3015, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 3012 of thereceiving system. Thereafter, the CAS software is operated in thereceiving system as an application program. According to an embodimentof the present invention, the CAS software is mounted on (or stored) ina middleware platform and, then executed. A Java middleware will begiven as an example of the middleware included in the present invention.Herein, the CAS software should at least include information requiredfor the authentication process and also information required for thedescrambling process.

Therefore, the authentication unit 3008 performs authenticationprocesses between the transmitting system and the receiving system andalso between the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 3008 compares the standardized serial numberincluded in the memory card with the unique information of the receivingsystem, thereby performing the authentication process between thereceiving system and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 3015, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 3012 upon the shipping of the presentinvention, or be downloaded to the first memory 3012 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 3016 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 3003, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 3004 and 3007. More specifically, theCAS software operating in the Java middleware platform first reads outthe unique (or serial) number of the receiving system from thecorresponding receiving system and compares it with the unique number ofthe receiving system transmitted through the EMM, thereby verifyingwhether the receiving system is entitled to receive the correspondingdata. Once the receiving entitlement of the receiving system isverified, the corresponding broadcasting service information transmittedto the ECM and the entitlement of receiving the correspondingbroadcasting service are used to verify whether the receiving system isentitled to receive the corresponding broadcasting service. Once thereceiving system is verified to be entitled to receive the correspondingbroadcasting service, the authentication key transmitted to the EMM isused to decode (or decipher) the encoded CW, which is transmitted to theECM, thereby transmitting the decoded CW to the descramblers 3004 and3007. Each of the descramblers 3004 and 3007 uses the CW to descramblethe broadcasting service.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiving system,as long as an external memory interface is provided, the presentinvention may embody a CAS system that can meet the requirements of alltypes of memory card that may be detachably fixed to the receivingsystem. Thus, the present invention may realize maximum performance ofthe receiving system with minimum fabrication cost, wherein thereceiving system may receive paid broadcasting contents such asbroadcast programs, thereby acknowledging and regarding the variety ofthe receiving system. Moreover, since only the minimum applicationprogram interface is required to be embodied in the embodiment of thepresent invention, the fabrication cost may be minimized, therebyeliminating the manufacturer's dependence on CAS manufacturers.Accordingly, fabrication costs of CAS equipments and management systemsmay also be minimized.

Meanwhile, the descramblers 3004 and 3007 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 3018, the received data may bedescrambled and then stored, or stored in the memory at the point ofbeing received and then descrambled later on prior to being played (orreproduced). Thereafter, in case scramble/descramble algorithms areprovided in the storage controller 3017, the storage controller 3017scrambles the data that are being received once again and then storesthe re-scrambled data to the third memory 3018.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 3019. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 3019 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 3019 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module3019. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1×EV-DO, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 3019.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 3003 receives either the real-time data outputted from thedemodulating unit 3002 or the data read from the third memory 3018,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 3003 performs demultiplexing on theenhanced data packet. Similar process steps have already been describedearlier in the description of the present invention. Therefore, adetailed of the process of demultiplexing the enhanced data will beomitted for simplicity.

The first descrambler 3004 receives the demultiplexed signals from thedemultiplexer 3003 and then descrambles the received signals. At thispoint, the first descrambler 3004 may receive the authentication resultreceived from the authentication unit 3008 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 3005 and the video decoder 3006 receive the signalsdescrambled by the first descrambler 3004, which are then decoded andoutputted. Alternatively, if the first descrambler 3004 did not performthe descrambling process, then the audio decoder 3005 and the videodecoder 3006 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 3007 and processed accordingly.

As described above, the DTV receiving system and method of processingbroadcast signal in the DTV receiving system according to the presentinvention has the following advantages. More specifically, the DTVreceiving system and method of processing broadcast signal in the DTVreceiving system according to the present invention is highly protectedagainst (or resistant to) any error that may occur when transmittingsupplemental data through a channel. And, the present invention is alsohighly compatible to the conventional VBS receiving system. Moreover,the present invention may also receive the supplemental data without anyerror even in channels having severe ghost effect and noise.

Additionally, the transmitting system of the present inventionconfigures the enhanced data packet to include at least any one of theenhanced data, which include information, and the known data, which areknown by the transmitting system and the receiving system, and transmitsthe configured enhanced data packet. The receiving system used the knowndata for channel equalization, thereby enhancing the receivingperformance. Particularly, when the plurality of enhanced data packetsare transmitted in hierarchically differentiated areas, the CIR of eacharea is estimated in accordance with the characteristic of each area, soas to perform channel equalization, thereby enhancing the channelequalizing performance. Furthermore, the present invention is even moreeffective when applied to mobile and portable receivers, which are alsoliable to a frequent change in channel and which require protection (orresistance) against intense noise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed:
 1. A method of processing a broadcast signal in abroadcast receiving system, the method comprising: receiving thebroadcast signal comprising service data for a service, known data thatis known to the broadcast receiving system, first signaling information,and second signaling information, wherein the first signalinginformation includes channel information of the service, wherein thesecond signaling information includes information for acquisition of theservice, wherein information for acquisition of the first signalinginformation is fixed, wherein information for acquisition of the secondsignaling information is variable, and wherein the service data aredelivered using a specific protocol; demodulating the received broadcastsignal; equalizing the demodulated broadcast signal by performingchannel estimation based on the known data; decoding the service data inthe equalized broadcast signal for forward error correction; andproviding the service of the decoded service data based on at least oneof the first signaling information or the second signaling informationin the broadcast signal.
 2. The method of claim 1, further comprising:storing at least one of the first signaling information or the secondsignaling information into a channel map.
 3. The method of claim 2,further comprising: updating the channel map based on at least one ofthe first signaling information or the second signaling information. 4.A broadcast receiving system for processing a broadcast signal, thebroadcast receiving system comprising: a tuner to receive the broadcastsignal comprising service data for a service, known data that is knownto the broadcast receiving system, first signaling information, andsecond signaling information, wherein the first signaling informationincludes channel information of the service, wherein the secondsignaling information includes information for acquisition of theservice, wherein information for acquisition of the first signalinginformation is fixed, wherein information for acquisition of the secondsignaling information is variable, and wherein the service data aredelivered using a specific protocol; a demodulator to demodulate thereceived broadcast signal; an equalizer to equalize the demodulatedbroadcast signal by performing channel estimation based on the knowndata; a decoder to decode the service data in the equalized broadcastsignal for forward error correction; and a manager to provide theservice of the decoded service data based on at least one of the firstsignaling information or the second signaling information in thebroadcast signal.
 5. The broadcast receiving system of claim 4, whereinthe manager stores at least one of the first signaling information orthe second signaling information into a channel map.
 6. The broadcastreceiving system of claim 5, wherein the manager updates the channel mapbased on at least one of the first signaling information or the secondsignaling information.